I have my system running on a RAID 1 setup through a PCI RAID card. I have 2 Identical 1TB drives with Windows XP installed.(It's a Siig SATA II-150 PCI RAID card By the way.)

So recently I started getting a S.M.A.R.T. error on boot:

OK, so one of the drives is failing... but which one? They're still under warranty, but I need to figure out which one is bad so I can send it back.

The RAID BIOS is no help:

If I try to rebuild, it tells me the RAID is Good.If I try to verify the RAID, it fails.

So... Here's some gobbledeegook just in case it's useful:Should be simple, right?Both drives are identical and plugged into the same PCI card.How can I tell which of my 2 identical drives is the failing one?

The drive connected to SATA port 5 is at fault. Backup and replace it immediately.

Actually reading that further, it's not as clear as it sounds...
The only way you'd know for sure is to pull one, see if it's still BAD, then swap and pull the other to make sure.
Don't leave more than 1 drive off or you'll fail the entire array.

The Drive on SATA Port 5 has a SMART Failure or one of the attributes have been exceeded.. I'd try something like CrystalDiskInfo and take a look

I've had my BIOS report SMART Failure on my 7 year old WD Raptor... turn's out one sector was bad and it was stuck trying to read/write to it - Ran spinrite on it, Sector was marked bad and now it shows SMART: STATUS WARNING...

I just don't keep anything I wouldn't want to lose on it (Mostly Games/Screenshots and Game captures)

Fraz is right. The SMART warning only shows that the device will fail, not has failed, so it makes sense that the RAID is healthy (for now). That said, with some of these cheap RAID cards, you do have to let the drive fail first to know for sure (I bet the BIOS is misreporting the SATA channel unless there is another HDD you didn't mention - so if your mobo has 4 channels its prob Ch0 on the card).

Fraz is right. The SMART warning only shows that the device will fail, not has failed, so it makes sense that the RAID is healthy (for now). That said, with some of these cheap RAID cards, you do have to let the drive fail first to know for sure (I bet the BIOS is misreporting the SATA channel unless there is another HDD you didn't mention - so if your mobo has 4 channels its prob Ch0 on the card).

That's not what's happening. He's getting an error from port 5 on the motherboard. His raid is separate from the motherboard, it's on its own PCI controller. The drives attached to the raid controller are fine, Whatever is attached to port 5 on the motherboard has the smart error.

That's not what's happening. He's getting an error from port 5 on the motherboard. His raid is separate from the motherboard, it's on its own PCI controller. The drives attached to the raid controller are fine, Whatever is attached to port 5 on the motherboard has the smart error.

If you look at the Drive WL1000GSA1672E is different than the WD models listed in the RAID

That's not what's happening. He's getting an error from port 5 on the motherboard. His raid is separate from the motherboard, it's on its own PCI controller. The drives attached to the raid controller are fine, Whatever is attached to port 5 on the motherboard has the smart error.

Agree with above, it is the 'IDE Drive' plugged into SATA Port 5 that has an issue, not the drives that make up the RAID Array

That's not what's happening. He's getting an error from port 5 on the motherboard. His raid is separate from the motherboard, it's on its own PCI controller. The drives attached to the raid controller are fine, Whatever is attached to port 5 on the motherboard has the smart error.

Which is why I asked if there was a third HDD that the OP didn't mention, since that does appear to be the obvious error. The serial also points to a MediaMax HDD (whatever that is).